1. Field of the Invention
The present invention relates to an improved outer tube structure for flexible tubes.
2. Description of the Related Art
FIGS. 5 and 6 of the drawings illustrate a prior art flexible tube in which an inner tube 30 is wound around by a protective tube 31. Between the inner tube 30 and the outer tube 31, a metallic strip 32 and a string 33 are helically wound to reinforce the structure. However, as shown in FIG. 6, a considerable gap exists between the strip 32 and the string 33 such that the flexible tube is deformed and bent and thus blocked when subjected to an external force. As a result, fluid or gas, which is delivered by the flexible tube, cannot pass. In addition, the bent area of the flexible tube cannot return to its original shape after the external force has been removed. Further, the metallic strip 32 may pierce the inner tube, which is usually made of rubber.
FIG. 7 illustrates another prior art flexible tube which includes a metallic outer strip 41 wound around a rubber inner tube 40. The outer strip 41 includes complimentarily shaped protrusion and recess defined in an outer side and an inner side thereof, respectively. Nevertheless, when the flexible tube is subjected to a relatively large load or is bent by a relatively large angle, the metallic outer strip 41 will be deformed and thus cause irrecoverable damage to the inner tube 40. Further, the rubber inner tube 40 also tends to be pierced by the metallic strip 41.
FIG. 8 illustrates a further prior art flexible tube which includes an inner rubber tube 50 covered by a steel net 51, which is time-consuming and costly. In addition, the bend-resistant effect and the shape recovery capability are found unsatisfactory.
The present invention is intended to provide an improved outer tube structure which mitigates and/or obviates the above-mentioned problems.